OS X 10.12 is expected to ship in the third or fourth quarter.
9to5Mac says Siri for OS X will be packaged in a "polished" user-interface and will be launched from the Mac's menu bar where the volume, Wi-Fi, and other utilities can be launched from. When a user clicks the Siri button, a transparent Siri interface will appear in the top right corner of the screen.
OS X 10.12 will also feature minor user interface tweaks, the site says.
Further, Apple is expected to take the wraps off iOS 10 at the conference, used by Apple to show developers the latest version of its software across its device lineup.